The present invention relates to an electrode assembly for an electrostatic moisture meter for powdery or granular material.
Various methods have been proposed for taking measurement of the water content of powdery or granular material, among which is an electrostatic method. In this method, the electrostatic capacity between a high-tension electrode and an earth electrode with a powdery material therebetween is measured. The thus obtained capacity measurement is in turn converted into a measurement of the water content in accordance with the proportionality of the capacity of the material to the water content thereof.
A conventional electrode assembly is shown in FIG. 1. The assembly includes a cylindrical insulator 3 of Bakelite, for example, a high-tension electrode 1, earth electrodes 2 both secured on the inner face of the insulator, and a guard electrode 4' on the outer face of the insulator. This electrode assembly, however, has some disadvantages. One of the most important disadvantages is related to the shape of the assembly. As is apparent, it is not easy to insert the electrode assembly into a powdery material under measurement since the assembly has a cylindrical form. Upon insertion, the electrode assembly may cause a change of the state of the material and make an unstable contact therewith to provide an inaccurate measurement since the electrodes involved have a large surface area. A further disadvantage in the prior electrode assembly is that it has a large stray capacity which also makes an accurate measurement of the capacity of the material difficult.